Expanding tubulars has come in vogue in many downhole applications. In a monobore well the finished size of the casing is the same. This is accomplished by inserting casing of a given size and expanding it downhole into a sealing relationship with the previous length of casing already in the bore so that a constant internal clearance diameter, known as drift diameter, is maintained. The drift diameter controls the size of tools that may later be advanced through the expanded tubular string. There are many other applications of expansion technology. Liner strings are hung on casing. Patches for cracked or broken casing or liner are patched with sleeves expanded downhole. Gravel pack screens are expanded to eliminate the annular space previously used for depositing gravel to retard production of sand.
With the ever-increasing use of expanding techniques there comes an undesirable side effect that has not been addressed. As a result of expansion of a given length of tube to a predetermined inside diameter using a swage, for example, the ends of the tubular tended to curl or flex inwardly toward the center of the expanded tubular. This phenomenon will reduce the drift diameter. This reduction in drift diameter could create a variety of problems. It could reduce production rates. It could make it impossible to pass certain tools to a desired location. It could create erosion areas where a portion of the tubular extended into the flowing stream that may eventually lead to tubular leakage. This reduction of the drift diameter as a result of expansion is referred to as the “end effect” in this application.
The present invention seeks to minimize or eliminate this end effect in several ways. One approach is to weaken the end in a variety of ways to counteract the forces acting on it to make it bend in after expansion. Another approach of the present invention is to pre-bend the ends outwardly so that the end effect nets a result of no reduction in drift diameter. Another approach of the present invention is to employ a soft material near the ends during swaging. Thereafter, even if there is some end effect, the material reducing the drift diameter is soft enough so that flow or a tool that needs to pass simply removes or cuts off any of the soft material that stands in the way. These and other approaches to minimizing or otherwise dealing with the end effect issue will be more readily apparent to those skilled in the art from a review of the description of the preferred embodiment and the claims, which appear below.
Generally related to the field of expanding sleeves in tubulars or expanding tubular ends are U.S. Pat. No. 2,623,570; 3,712,376; 3,746,091; 6,155,092 and 6,412,324. Of these, the most relevant is the '091 patent FIGS. 5 and 9 showing overlapping flexible fingers 55 at the end of a tubular sleeve 13 being expanded and at the end of a hold down sleeve 57. These overlapping fingers are pushed out to let the swage 15 pass and then spring back to their original position as described at Column 4 Lines 42-50. This application does not deal with end effect issues.